Radiolytic synthesis of iridium nanoparticles onto carbon nanotubes

Iridium nanoparticles on multiwalled carbon nanotubes were synthesized in a single-step process by gamma irradiation from a cobalt-60 source. These particles were prepared at various absorbed doses, precursors, and surfactant concentrations. The nanoparticles were homogeneously distributed onto the nanotubes' surface with average particle sizes between 2 and 5 nm. The particle size was found to decrease from 4.5 to 3.4 nm, when the absorbed dose increased from 20 to 60 kGy. An increase in the surfactant concentration also reduced the particle size from 3.8 to 2.5 nm. No significant variation in particle size was observed when the precursor concentration was increased. Although no Iridium-Carbon bonds were detected by X-ray Photoelectron Spectroscopy, Iridium-Oxigen bonds were observed. The interaction between the nanoparticles and the nanotubes seems to occur through oxygenated sites on the nanotubes' surface.